Metrics: Create a widget to enable changing the period of metrics
In metrics, it is now possible to specify what time frame the metrics should be displayed for, and with what granularity (hour, day, week, month, ...) (introduced by #44 (closed)).
As an example, you can specify period={"count": 12, "period": "month", "end_date": "2019-10-23"}
which will show you metrics for every month for the past year starting from 2019-10-31. See Periodizer.from_json() for the full spec.
As writing the above example by hand in the URL bar is a little cumbersome, let's write some JS widget that would generate this for us in all the metrics pages. The widget should be a single line and relatively discrete.